Compositions and methods for planarizing or polishing the surface of a substrate are well known in the art. Polishing compositions (also known as polishing slurries) typically contain an abrasive material in a liquid carrier and are applied to a surface by contacting the surface with a polishing pad saturated with the polishing composition. Typical abrasive materials include silicon dioxide, cerium oxide, aluminum oxide, zirconium oxide, and tin oxide. Polishing compositions are typically used in conjunction with polishing pads (e.g., a polishing cloth or disk). Instead of, or in addition to, being suspended in the polishing composition, the abrasive material may be incorporated into the polishing pad.
The next generation of semiconductor devices incorporates the use of materials with greater hardness and other desirable properties for high power, high temperature, and high frequency operation applications. Such materials include silicon carbide and silicon nitride. Silicon carbide is a material with a desirable combination of electrical and thermo-physical properties, including high practical operating temperature, good corrosion resistance, and high thermal properties. Silicon nitride is a high strength hard material having utility as an etch stop mask, an electrical insulator, a chemical diffusion barrier, or as a dielectric material in capacitors. However, silicon carbide and silicon nitride are significantly harder and more chemically inert than other materials comprising integrated circuits.
In addition, known polishing compositions and methods do not provide the ability to selectively remove silicon carbide from a semiconductor wafer without removing materials such as silicon dioxide from the same wafer at unacceptably high levels. As the technology for integrated circuit devices advances, traditional materials are being used in new and different ways to achieve the level of performance needed for advanced integrated circuits. In particular, silicon nitride, silicon carbide, and silicon dioxide are being used in various combinations to achieve new and even more complex device configurations. In general, the structural complexity and performance characteristics vary across different applications.
Accordingly, there is an ongoing need to develop new polishing methods and compositions that provide relatively high rates of removal of silicon carbide and to selectively remove silicon carbide in preference to other materials present on the surface of the semiconductor wafer.